md/raid5 uses the plugging infrastructure provided by the block layer
and 'struct request_queue'.  However when we plug raid5 under dm there
is no request queue so we cannot use that.

So create a similar infrastructure that is much lighter weight and use
it for raid5.
Signed-off-by: NNeilBrown <neilb@suse.de>

the dm module will need this for dm-raid45.

Also only access ->queue->backing_dev_info->congested_fn
if ->queue actually exists.  It won't in a dm target.
Signed-off-by: NNeilBrown <neilb@suse.de>

dm-raid456 does not provide a 'queue' for raid5 to use,
so we must make raid5 stop depending on the queue.

First: read_ahead
dm handles read-ahead adjustment fully in userspace, so
simply don't do any readahead adjustments if there is
no queue.

Also re-arrange code slightly so all the accesses to ->queue are
together.

Finally, move the blk_queue_merge_bvec function into the 'if' as
the ->split_io setting in dm-raid456 has the same effect.
Signed-off-by: NNeilBrown <neilb@suse.de>

We will shortly allow md devices with no gendisk (they are attached to
a dm-target instead).  That will cause mdname() to return 'mdX'.
There is one place where mdname really needs to be unique: when
creating the name for a slab cache.
So in that case, if there is no gendisk, you the address of the mddev
formatted in HEX to provide a unique name.
Signed-off-by: NNeilBrown <neilb@suse.de>

Separate the actual 'change' code from the sysfs interface
so that it can eventually be called internally.
Signed-off-by: NNeilBrown <neilb@suse.de>

We will want md devices to live as dm targets where sysfs is not
visible.  So allow md to not connect to sysfs.
Signed-off-by: NNeilBrown <neilb@suse.de>

There are few situations where it would make any sense to add a spare
when reducing the number of devices in an array, but it is
conceivable:  A 6 drive RAID6 with two missing devices could be
reshaped to a 5 drive RAID6, and a spare could become available
just in time for the reshape, but not early enough to have been
recovered first.  'freezing' recovery can make this easy to
do without any races.

However doing such a thing is a bad idea.  md will not record the
partially-recovered state of the 'spare' and when the reshape
finished it will think that the spare is still spare.
Easiest way to avoid this confusion is to simply disallow it.
Signed-off-by: NNeilBrown <neilb@suse.de>

As the comment says, the tail of this loop only applies to devices
that are not fully in sync, so if In_sync was set, we should avoid
the rest of the loop.

This bug will hardly ever cause an actual problem.  The worst it
can do is allow an array to be assembled that is dirty and degraded,
which is not generally a good idea (without warning the sysadmin
first).

This will only happen if the array is RAID4 or a RAID5/6 in an
intermediate state during a reshape and so has one drive that is
all 'parity' - no data - while some other device has failed.

This is certainly possible, but not at all common.
Signed-off-by: NNeilBrown <neilb@suse.de>

During a recovery of reshape the early part of some devices might be
in-sync while the later parts are not.
We we know we are looking at an early part it is good to treat that
part as in-sync for stripe calculations.

This is particularly important for a reshape which suffers device
failure.  Treating the data as in-sync can mean the difference between
data-safety and data-loss.
Signed-off-by: NNeilBrown <neilb@suse.de>

When we are reshaping an array, the device failure combinations
that cause us to decide that the array as failed are more subtle.

In particular, any 'spare' will be fully in-sync in the section
of the array that has already been reshaped, thus failures that
affect only that section are less critical.

So encode this subtlety in a new function and call it as appropriate.

The case that showed this problem was a 4 drive RAID5 to 8 drive RAID6
conversion where the last two devices failed.
This resulted in:

  good good good good incomplete good good failed failed

while converting a 5-drive RAID6 to 8 drive RAID5
The incomplete device causes the whole array to look bad,
bad as it was actually good for the section that had been
converted to 8-drives, all the data was actually safe.
Reported-by: NTerry Morris <tbmorris@tbmorris.com>
Signed-off-by: NNeilBrown <neilb@suse.de>

When an array is reshaped to have fewer devices, the reshape proceeds
from the end of the devices to the beginning.

If a device happens to be non-In_sync (which is possible but rare)
we would normally update the ->recovery_offset as the reshape
progresses. However that would be wrong as the recover_offset records
that the early part of the device is in_sync, while in fact it would
only be the later part that is in_sync, and in any case the offset
number would be measured from the wrong end of the device.

Relatedly, if after a reshape a spare is discovered to not be
recoverred all the way to the end, not allow spare_active
to incorporate it in the array.

This becomes relevant in the following sample scenario:

A 4 drive RAID5 is converted to a 6 drive RAID6 in a combined
operation.
The RAID5->RAID6 conversion will cause a 5 drive to be included as a
spare, then the 5drive -> 6drive reshape will effectively rebuild that
spare as it progresses.  The 6th drive is treated as in_sync the whole
time as there is never any case that we might consider reading from
it, but must not because there is no valid data.

If we interrupt this reshape part-way through and reverse it to return
to a 5-drive RAID6 (or event a 4-drive RAID5), we don't want to update
the recovery_offset - as that would be wrong - and we don't want to
include that spare as active in the 5-drive RAID6 when the reversed
reshape completed and it will be mostly out-of-sync still.
Signed-off-by: NNeilBrown <neilb@suse.de>

The entries in the stripe_cache maintained by raid5 are enlarged
when we increased the number of devices in the array, but not
shrunk when we reduce the number of devices.
So if entries are added after reducing the number of devices, we
much ensure to initialise the whole entry, not just the part that
is currently relevant.  Otherwise if we enlarge the array again,
we will reference uninitialised values.

As grow_buffers/shrink_buffer now want to use a count that is stored
explicity in the raid_conf, they should get it from there rather than
being passed it as a parameter.
Signed-off-by: NNeilBrown <neilb@suse.de>

By the previous modification, the cpu notifier can return encapsulate
errno value.  This converts the cpu notifiers for raid5.
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix: Raid-6 was not trying to correct a read-error when in
singly-degraded state and was instead dropping one more device, going to
doubly-degraded state. This patch fixes this behaviour.
Tested-by: NJanos Haar <janos.haar@netcenter.hu>
Signed-off-by: NGabriele A. Trombetti <g.trombetti.lkrnl1213@logicschema.com>
Reported-by: NJanos Haar <janos.haar@netcenter.hu>
Signed-off-by: NNeilBrown <neilb@suse.de>
Cc: stable@kernel.org

Many 'printk' messages from the raid456 module mention 'raid5' even
though it may be a 'raid6' or even 'raid4' array.  This can cause
confusion.
Also the actual array name is not always reported and when it is
it is not reported consistently.

So change all the messages to start:
    md/raid:%s:
where '%s' becomes e.g. md3 to identify the particular array.
Signed-off-by: NNeilBrown <neilb@suse.de>

For consistency allow raid4 to takeover raid0 in addition to raid5 (with a
raid4 layout).
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

We used to pass the personality make_request function direct
to the block layer so the first argument had to be a queue.
But now we have the intermediary md_make_request so it makes
at lot more sense to pass a struct mddev_s.
It makes it possible to have an mddev without its own queue too.
Signed-off-by: NNeilBrown <neilb@suse.de>

We set ->changed to 1 and call check_disk_change at the end
of md_open so that bd_invalidated would be set and thus
partition rescan would happen appropriately.

Now that we call revalidate_disk directly, which sets bd_invalidates,
that indirection is no longer needed and can be removed.
Signed-off-by: NNeilBrown <neilb@suse.de>

While I generally prefer letting personalities do as much as possible,
given that we have a central md_make_request anyway we may as well use
it to simplify code.
Also this centralises knowledge of ->gendisk which will help later.
Signed-off-by: NNeilBrown <neilb@suse.de>

Diving through ->queue to find mddev is unnecessarily complex - there
is an easier path to finding mddev, so use that.
Signed-off-by: NNeilBrown <neilb@suse.de>

This is unlikely to be wanted, but we may as well provide it
for completeness.
Signed-off-by: NNeilBrown <neilb@suse.de>

Signed-off-by: NMaciej Trela <maciej.trela@intel.com>
Signed-off-by: NNeilBrown <neilb@suse.de>

void pointers do not need to be cast to other pointer types.
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: NNeilBrown <neilb@suse.de>

Some levels expect the 'redundancy group' to be present,
others don't.
So when we change level of an array we might need to
add or remove this group.

This requires fixing up the current practice of overloading ->private
to indicate (when ->pers == NULL) that something needs to be removed.
So create a new ->to_remove to fill that role.

When changing levels, we may need to add or remove attributes.  When
changing RAID5 -> RAID6, we both add and remove the same thing.  It is
important to catch this and optimise it out as the removal is delayed
until a lock is released, so trying to add immediately would cause
problems.


Cc: stable@kernel.org
Signed-off-by: NNeilBrown <neilb@suse.de>

Fix: Raid-6 was not trying to correct a read-error when in
singly-degraded state and was instead dropping one more device, going to
doubly-degraded state. This patch fixes this behaviour.
Tested-by: NJanos Haar <janos.haar@netcenter.hu>
Signed-off-by: NGabriele A. Trombetti <g.trombetti.lkrnl1213@logicschema.com>
Reported-by: NJanos Haar <janos.haar@netcenter.hu>
Signed-off-by: NNeilBrown <neilb@suse.de>
Cc: stable@kernel.org

Previous patch changes stripe and chunk_number to sector_t but
mistakenly did not update all of the divisions to use sector_dev().

This patch changes all the those divisions (actually the '%' operator)
to sector_div.
Signed-off-by: NNeilBrown <neilb@suse.de>
Cc: stable@kernel.org
Tested-by: NStefan Lippers-Hollmann <s.l-h@gmx.de>

With many large drives and small chunk sizes it is possible
to create a RAID5 with more than 2^31 chunks.  Make sure this
works.
Reported-by: NBrett King <king.br@gmail.com>
Signed-off-by: NNeilBrown <neilb@suse.de>
Cc: stable@kernel.org

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files.  percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed.  Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability.  As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

  http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
  only the necessary includes are there.  ie. if only gfp is used,
  gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
  blocks and try to put the new include such that its order conforms
  to its surrounding.  It's put in the include block which contains
  core kernel includes, in the same order that the rest are ordered -
  alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
  doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
  because the file doesn't have fitting include block), it prints out
  an error message indicating which .h file needs to be added to the
  file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
   over 4000 files, deleting around 700 includes and adding ~480 gfp.h
   and ~3000 slab.h inclusions.  The script emitted errors for ~400
   files.

2. Each error was manually checked.  Some didn't need the inclusion,
   some needed manual addition while adding it to implementation .h or
   embedding .c file was more appropriate for others.  This step added
   inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
   from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
   e.g. lib/decompress_*.c used malloc/free() wrappers around slab
   APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
   editing them as sprinkling gfp.h and slab.h inclusions around .h
   files could easily lead to inclusion dependency hell.  Most gfp.h
   inclusion directives were ignored as stuff from gfp.h was usually
   wildly available and often used in preprocessor macros.  Each
   slab.h inclusion directive was examined and added manually as
   necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
   were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
   distributed build env didn't work with gcov compiles) and a few
   more options had to be turned off depending on archs to make things
   build (like ipr on powerpc/64 which failed due to missing writeq).

   * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
   * powerpc and powerpc64 SMP allmodconfig
   * sparc and sparc64 SMP allmodconfig
   * ia64 SMP allmodconfig
   * s390 SMP allmodconfig
   * alpha SMP allmodconfig
   * um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
   a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: NTejun Heo <tj@kernel.org>
Guess-its-ok-by: NChristoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>

Except for SCSI no device drivers distinguish between physical and
hardware segment limits.  Consolidate the two into a single segment
limit.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Add __percpu sparse annotations to places which didn't make it in one
of the previous patches.  All converions are trivial.

These annotations are to make sparse consider percpu variables to be
in a different address space and warn if accessed without going
through percpu accessors.  This patch doesn't affect normal builds.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NBorislav Petkov <borislav.petkov@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Neil Brown <neilb@suse.de>

======
This fix is related to
    http://bugzilla.kernel.org/show_bug.cgi?id=15142
but does not address that exact issue.
======

sysfs does like attributes being removed while they are being accessed
(i.e. read or written) and waits for the access to complete.

As accessing some md attributes takes the same lock that is held while
removing those attributes a deadlock can occur.

This patch addresses 3 issues in md that could lead to this deadlock.

Two relate to calling flush_scheduled_work while the lock is held.
This is probably a bad idea in general and as we use schedule_work to
delete various sysfs objects it is particularly bad.

In one case flush_scheduled_work is called from md_alloc (called by
md_probe) called from do_md_run which holds the lock.  This call is
only present to ensure that ->gendisk is set.  However we can be sure
that gendisk is always set (though possibly we couldn't when that code
was originally written.  This is because do_md_run is called in three
different contexts:
  1/ from md_ioctl.  This requires that md_open has succeeded, and it
     fails if ->gendisk is not set.
  2/ from writing a sysfs attribute.  This can only happen if the
     mddev has been registered in sysfs which happens in md_alloc
     after ->gendisk has been set.
  3/ from autorun_array which is only called by autorun_devices, which
     checks for ->gendisk to be set before calling autorun_array.
So the call to md_probe in do_md_run can be removed, and the check on
->gendisk can also go.


In the other case flush_scheduled_work is being called in do_md_stop,
purportedly to wait for all md_delayed_delete calls (which delete the
component rdevs) to complete.  However there really isn't any need to
wait for them - they have already been disconnected in all important
ways.

The third issue is that raid5->stop() removes some attribute names
while the lock is held.  There is already some infrastructure in place
to delay attribute removal until after the lock is released (using
schedule_work).  So extend that infrastructure to remove the
raid5_attrs_group.

This does not address all lockdep issues related to the sysfs
"s_active" lock.  The rest can be address by splitting that lockdep
context between symlinks and non-symlinks which hopefully will happen.
Signed-off-by: NNeilBrown <neilb@suse.de>

This code was written long ago when it was not possible to
reshape a degraded array.  Now it is so the current level of
degraded-ness needs to be taken in to account.  Also newly addded
devices should only reduce degradedness if they are deemed to be
in-sync.

In particular, if you convert a RAID5 to a RAID6, and increase the
number of devices at the same time, then the 5->6 conversion will
make the array degraded so the current code will produce a wrong
value for 'degraded' - "-1" to be precise.

If the reshape runs to completion end_reshape will calculate a correct
new value for 'degraded', but if a device fails during the reshape an
incorrect decision might be made based on the incorrect value of
"degraded".

This patch is suitable for 2.6.32-stable and if they are still open,
2.6.31-stable and 2.6.30-stable as well.

Cc: stable@kernel.org
Reported-by: NMichael Evans <mjevans1983@gmail.com>
Signed-off-by: NNeilBrown <neilb@suse.de>

Suggested by  Oren Held <orenhe@il.ibm.com>
Signed-off-by: NNeilBrown <neilb@suse.de>

The post-barrier-flush is sent by md as soon as make_request on the
barrier write completes.  For raid5, the data might not be in the
per-device queues yet.  So for barrier requests, wait for any
pre-reading to be done so that the request will be in the per-device
queues.

We use the 'preread_active' count to check that nothing is still in
the preread phase, and delay the decrement of this count until after
write requests have been submitted to the underlying devices.
Signed-off-by: NNeilBrown <neilb@suse.de>

Previously barriers were only supported on RAID1.  This is because
other levels requires synchronisation across all devices and so needed
a different approach.
Here is that approach.

When a barrier arrives, we send a zero-length barrier to every active
device.  When that completes - and if the original request was not
empty -  we submit the barrier request itself (with the barrier flag
cleared) and then submit a fresh load of zero length barriers.

The barrier request itself is asynchronous, but any subsequent
request will block until the barrier completes.

The reason for clearing the barrier flag is that a barrier request is
allowed to fail.  If we pass a non-empty barrier through a striping
raid level it is conceivable that part of it could succeed and part
could fail.  That would be way too hard to deal with.
So if the first run of zero length barriers succeed, we assume all is
sufficiently well that we send the request and ignore errors in the
second run of barriers.

RAID5 needs extra care as write requests may not have been submitted
to the underlying devices yet.  So we flush the stripe cache before
proceeding with the barrier.

Note that the second set of zero-length barriers are submitted
immediately after the original request is submitted.  Thus when
a personality finds mddev->barrier to be set during make_request,
it should not return from make_request until the corresponding
per-device request(s) have been queued.

That will be done in later patches.
Signed-off-by: NNeilBrown <neilb@suse.de>
Reviewed-by: NAndre Noll <maan@systemlinux.org>

qd_idx is previously declared and given exactly the same value!
Signed-off-by: NNeilBrown <neilb@suse.de>

Normally is it not safe to allow a raid5 that is both dirty and
degraded to be assembled without explicit request from that admin, as
it can cause hidden data corruption.
This is because 'dirty' means that the parity cannot be trusted, and
'degraded' means that the parity needs to be used.

However, if the device that is missing contains only parity, then
there is no issue and assembly can continue.
This particularly applies when a RAID5 is being converted to a RAID6
and there is an unclean shutdown while the conversion is happening.

So check for whether the degraded space only contains parity, and
in that case, allow the assembly.
Signed-off-by: NNeilBrown <neilb@suse.de>

When a reshape finds that it can add spare devices into the array,
those devices might already be 'in_sync' if they are beyond the old
size of the array, or they might not if they are within the array.

The first case happens when we change an N-drive RAID5 to an
N+1-drive RAID5.
The second happens when we convert an N-drive RAID5 to an
N+1-drive RAID6.

So set the flag more carefully.
Also, ->recovery_offset is only meaningful when the flag is clear,
so only set it in that case.

This change needs the preceding two to ensure that the non-in_sync
device doesn't get evicted from the array when it is stopped, in the
case where v0.90 metadata is used.
Signed-off-by: NNeilBrown <neilb@suse.de>

This value is visible through sysfs and is used by mdadm
when it manages a reshape (backing up data that is about to be
rearranged).  So it is important that it is always correct.
Current it does not get updated properly when a reshape
starts which can cause problems when assembling an array
that is in the middle of being reshaped.

This is suitable for 2.6.31.y stable kernels.

Cc: stable@kernel.org
Signed-off-by: NNeilBrown <neilb@suse.de>

Signed-off-by: NDan Williams <dan.j.williams@intel.com>